1. Field of the Invention
This invention relates to a gas burner for a stove, and more particularly to a design for avoiding, by means of a simple construction, an extinguishment occurring when the quantity of gas is reduced rapidly from large fire to small fire.
2. Description of the Prior Art
Conventionally, an ordinary gas burner for a stove can adjust the quantity of gas from a large fire of about 2,700-4,000 kcal/h to a small fire of about 300-450 kcal/h. In a gas burner for a stove, air corresponding to the quantity of gas spouting from a nozzle is drawn by an ejector pump action caused by a flow velocity of the gas spouting from the nozzle. Primary air (about 50% of theoretical air) necessary for combustion is drawn. Thus, in a state of large fire, a large quantity of primary air is drawn according to the quantity of gas.
In adjusting heating power to a small fire from the state of large fire in which a large quantity of primary air is drawn as noted above, the quantity of gas is instantaneously reduced to a state of small fire. The flow of primary air drawn in the state of large fire itself has an inertial action. When the quantity of gas is reduced rapidly, the primary air changes with a delay after the instantaneous change in the quantity of gas, whereby the primary air momentarily becomes excessive. In such an air rich state, combustion cannot be continued. There has been a problem that the fire goes out.
To solve such a problem, as in Patent Laying-Open Publication H3-36418 shown in FIG. 6, a diaphragm 8 is provided at a forward end of a branch passage 7 branched from a gas passage 13 extending to a nozzle 6 for jetting gas into a mixing tube 55, to form an expansion/contraction chamber 9 which expands and contracts under gas pressures transmitted. When throttled from a state of large fire to a state of small fire, the expansion/contraction chamber 9 expands as a result of a pressure drop, to push the gas stored through the branch passage 7 out to the gas passage 13, thereby to compensate for a lack in the gas flow rate due to the rapid throttle-down. Numeral 30 in the drawing denotes a valve for adjusting the quantity of gas.
However, such a construction additionally requires movable parts such as the diaphragm 8 and a balancing spring 10 for supporting the diaphragm 8. The balancing spring 10 must be incorporated with predetermined precision. The construction and assembly are complicated. As another device, though not shown in the drawings, a curved path in the shape of letter L is formed in a control path of a control lever for adjusting the quantity of gas, so that the control lever cannot move from a large fire position to a small fire position at a stroke. However, this construction requires the approximately L-shaped curved path in the control path. Moreover a control side including the control lever needs a construction corresponding to the movement of the control lever moving through the curved path. Thus, the construction is complicated.
As a further device, a damper for adjusting primary air for a burner is turned in response to a movement of a control lever for adjusting the quantity of gas. In time of throttling to a state of small fire, the quantity of primary air also is throttled down. However, such a construction requires the damper to be pivotable, and a complicated structure for its interlocking with the control lever, which lowers assembling facility.
Thus, the prior art has the problems of requiring movable parts, and of complicated construction and assembly, high cost and low productivity.